Time-dependent and spatiotemporal statistical analysis of intraplate anomalous seismicity: Sarria-Triacastela-Becerreá (NW Iberian Peninsula, Spain)

SUMMARY The Sarria-Triacastela-Becerreá seismicity is located in an intraplate region considered seismically stable, but 1995 started unprecedented earthquake activity the area. Since then anomalous long-term continuous remains until now same location. Despite and large magnitudes for standards (5.1 Mw), origin mechanisms of this unclear. isolation background from main shock–aftershock contribution by means application Epidemic Type Aftershock Sequences (ETAS) model, spatial depiction resemblance to near seismic regions allow us identify several behaviours. From 1998/99, location mainly consists intensive deeper sequences linked 1997 shocks. Our results suggest that shocks triggered aftershocks additionally initiated or facilitated aseismic processes. A likely scenario broke a sealed source at depth allowing subsequent intrusion high-pressurized fluids depth. period with Zamora characteristics proposes Triacastela was also tectonic activity. 1998/99 2018, change observed, took control swarm-type predominant. While rate decreases, relative goes up. Actually, after 2013 clusters almost disappear achieves 55 per cent total migration southeast upward trend shallower support fluid as possible driving mechanism responsible transient period. later periods b-values Ponte Caldelas Ventaniella related reactivation fractured areas. We propose mix different mechanisms, starting seismicity, generated during sequences, which through crustal fault patches, observed 1998–1999, following 20 yr.